1. Field of the Invention
This invention relates to a numerical controller, and particularly relate to a numerical controller that controls a feed rate based on a machining condition of a cutting tool.
2. Description of the Related Art
Such as grooving, free-form surface machining, side milling, incline machining, etc., with using a machine tool, there is a machining method of cutting a workpiece in a different direction from a direction of the spindle axis, to which a tool such as a milling tool, an end mill tool, etc. is attached, (Japanese Patent Laid-Open No. 2016-066201). For example, in side grooving using an end mill tool 2, a groove is machined by performing cutting feed on the end mill tool 2 attached to the spindle axis and rotated in a direction substantially orthogonal to the direction of the spindle axis as illustrated in FIG. 4 or performing cutting feed on the end mill tool 2 attached to the spindle axis and rotated parallel to a surface of a workpiece in a state of being cut deep into the workpiece as illustrated in FIG. 5. In addition, in ramping grooving using the end mill tool 2, as illustrated in FIG. 6, a groove is formed by performing cutting feed on the end mill tool 2 attached to the spindle axis and rotated such that the end mill tool 2 cuts deep into a surface of a workpiece on a slant.
In free-form surface machining using a ball end mill tool 4, as illustrated in FIG. 7, a curved surface is machined by performing cutting feed on the ball end mill tool 4 attached to a spindle axis and rotated in a different direction from a direction of the spindle axis (for example, a direction along a target free-form surface). In addition, in side milling using the end mill tool 2, as illustrated in FIG. 8, a side surface of a workpiece is machined by performing cutting feed on the end mill tool 2 attached to the spindle axis and rotated parallel to the side surface in a state of being cut into the workpiece.
As described above, most of cutting tools such as milling tools, end mill tools, etc. are provided with one or a plurality of blades on a side surface of the tool, etc. However, regardless of a single blade or a plurality of blades, in the machining method exemplified above, when a cutting operation is observed for only one blade, a workpiece is machined when a blade is brought into contact with the workpiece by rotational motion of a spindle axis (a rotation direction of the spindle axis) and movement in a different direction from a direction of the spindle axis. In particular, in a case of a tool provided with a plurality of blades, a workpiece is machined by each of the blades coming into contact with the workpiece by turns.
Further, for further understanding, milling illustrated in FIG. 9 will be described as an example. In the example of FIG. 9, six blades 6 are provided in a milling tool 5, and the blades 6 rotate in a rotation direction M of a spindle axis by rotational motion of the spindle axis. In addition, the milling tool 5 moves in a movement direction Q different from a direction of the spindle axis when a movement axis of the spindle axis is controlled. Further, when the blades 6 included in the milling tool 5 come into contact with a workpiece 3, the blades 6 move to the outside of the workpiece 3 while cutting the workpiece 3 due to rotational motion of the spindle axis and movement in the movement direction Q different from the direction of the spindle axis. When such operations are continuously performed, milling of the workpiece 3 using the six blades 6 included in the milling tool 5 is established. In such a machining method, a one-blade feed rate D indicating the amount of one-time machining per blade 6 included in the milling tool 5 may be calculated by Equation 1 below using the number of blades 6 included in the milling tool 5, the number of revolutions per unit time in the rotation direction M of the spindle axis, and a cutting feed rate in the movement direction Q. The one-blade feed rate may be calculated in the same method in each of the above-described machining methods.
                              ONE          ⁢                      -                    ⁢          BLADE          ⁢                                          ⁢          FEED          ⁢                                          ⁢          RATE          ⁢                                          ⁢          D                =                              CUTTING_FEED            ⁢                          _RATE              ⁢                                                          [                              m                ⁢                                  /                                ⁢                min                            ]                                                                                            NUMBER                  ⁢                                                                          ⁢                  OF                  ⁢                                                                          ⁢                  BLADES                  ×                  NUMBER                  ⁢                                                                          ⁢                  OF                                                                                                      REVOLUTIONS                  ⁢                                                                          ⁢                  OF                  ⁢                                                                          ⁢                  SPINDLE                  ⁢                                                                          ⁢                                      AXIS                    ⁢                                                                                  [                                          min                                              -                        1                                                              ]                                                                                                          [                  Equation          ⁢                                          ⁢          1                ]            
One-blade feed rate D
Cutting feed rate
Number of blades×Number of revolutions of the spindle axis
A recommended value set by a tool maker for each tool is provided for the one-blade feed rate of the tool, and an operator sets a machining condition including the cutting feed rate and the number of revolutions of the spindle axis while considering all factors related to cutting such as the recommended value of the one-blade feed rate described in a catalog of the tool maker, a machined shape of the workpiece, machining accuracy, a used machine, rigidity of tooling, etc. Here, when the operator erroneously sets the machining condition, and thus the one-blade feed rate exceeds the recommended value as a result, a decrease in machining quality of the workpiece, a drastic reduction in tool life, and damage to the tool may be caused.
As described above, at the time of determining the feed rate, the number of revolutions of the spindle axis, etc., the operator needs to be conscious of a recommended value of a cutting condition of the tool. However, there is a possibility of setting a machining condition which is not valid (does not satisfy the recommended value of the cutting condition) at the time of creating a new machining program. In addition, in a case of changing to a tool having the same shape (different coating and maker) with respect to an existing program, there is a possibility that, as a result of performing machining without changing the machining condition without checking a recommended value of a cutting condition of a new tool, machining not satisfying the recommended value of the cutting condition of the tool may be performed. Further, there is a possibility of performing machining not satisfying the recommended value of the cutting condition of the tool since the operator changes the number of revolutions of the spindle axis before machining or changes the number of revolutions of the spindle axis by operating an override, etc. during machining.